Twitter has fuelled speculation that it is preparing for an initial public offering by naming Cynthia Gaylor, a Morgan Stanley investment banker who has worked on deals for Facebook, LinkedIn and Zynga, as its head of corporate development.

The social media company announced the appointment in a tweet and Ms Gaylor responded in kind, saying that she looked forward to focusing on mergers and acquisitions and strategy at the company.

Millions of workers are in “precarious employment” that could be jeopardised by any further deterioration in the economy, government research suggests – with the smallest businesses most likely to be “hoarding” staff they no longer need.